1. Field of the Invention
The present invention relates to an optical information recording medium and a tracking servo method for the optical information recording medium in particular, an optical information recording medium of land/groove recording method in which the information is recorded both on a convex groove track called land and on a concave groove track called groove and which comprises a ROM area constructed with a pre-pit row previously formed on a basic substrate and a RAM area capable of being written additionally by the user both provided on a sheet of medium, and a tracking servo method for the above-mentioned optical information recording medium.
2. Description of the Related Art
As described in, for instance, Japanese Laid-open Patent Publication No. 6-76362/1994 entitled "AN OPTICAL DISK AND A METHOD OF MANUFACTURING IT", Japanese Laid-open Patent Publication No. 5-135362/1993 entitled "A MEMBER FOR RECORDING INFORMATION AND A RECORDING APPARATUS", and Japanese Laid-open Patent Publication No. 4-362526/1992 entitled "AN OPTICAL DISK" (as the conventional optical information recording medium, there has existed an optical information recording medium employing a land/groove recording method of recording the information both on the convex groove track called land and on the concave groove track called groove.
In the above-mentioned two laid-open patent applications; Japanese Laid-open Patent Publication No. 6-76362/1994 "AN OPTICAL DISK AND A METHOD OF MANUFACTURING IT" and Japanese Laid-open Patent Publication No. 5-135362/1993 "A MEMBER FOR RECORDING INFORMATION AND A RECORDING APPARATUS", the ROM area constructed with the pre-pit row previously formed on the basic substrate and the RAM area capable of being additionally written by the user on a sheet of medium are provided together in a sheet of medium.
Here, an optical information recording medium according to Japanese Laid-open Patent Publication No. 6-76362/1994 "AN OPTICAL DISK AND A METHOD OF MANUFACTURING IT" is explained, referring to FIG. 15. In this optical disk (optical information recording medium), the ROM area is constructed with the pre-pit rows, as shown in FIG. 15, and the RAM track area for additionally writing the information exists on the plain portion between the pre-pit rows. The address information needed at the time of additionally writing is constructed with the pre-pit on the ROM track and the additionally written record pit on the RAM track. For this reason, it is possible to reduce the cross-talk from the tracks adjacent to each other.
And further, only the pre-pit row on which the address information is formed is displaced (shifted) in the radius direction by 1/4 track pitch from the track center, and thereby it is possible for the ROM and the RAM to commonly occupy the address information constructed with one pre-pit row.
And further, the optical information recording medium according to Japanese Laid-open Patent Publication No. 5-135362/1993 "A MEMBER FOR RECORDING INFORMATION AND A RECORDING APPARATUS" is the one intending to reduce the cross-talk from the adjacent tracks by employing the ROM for either one of the land and the groove and employing the RAM for another thereof, as shown in FIG. 16. Moreover, in the above optical information recording medium, the address information of the ROM and that of the RAM are respectively arranged on the tracks constructed with the land and the groove respectively.
On the other hand, in Japanese Laid-open Patent Publication No. 4-362526/1992 "OPTICAL DISK", assuming that the pre-pit and the groove are arranged on the land and the groove depth of the pre-pit disposed on the land is Hp and that of the groove is Hg, a high modulation rate can be obtained by setting the groove depth of the pre-pit disposed on the tracking of the groove to (Hp+Hg) in case that the reproducing beam diameter is sufficiently narrower than the groove width.